A giant uses a willing person as a dildo. Emphasize the asphyxiation, the powerlessness, and the humiliation at being used as an object that the human dildo feels. If the person is being used vaginally, make sure to include descriptions of fluids flooding their face and waterboarding them, and if used anally, make sure to emphasize the suffocating tightness that would come with having their head in another person's asshole.